Protective system for transmission lines



Julie 4, 1929. J. SESSINGHAUS 1,715,679

PROTECTIVE SYSTEM FOR TRANSMISSION LINES Filed March 27, 1925 //VVE/V 70 R Johan/1 es Sass in /1 aus Patented June 4, 1929.

T UNITEDISTATES PATENT. OFFICE.

JOHANNES S ESSINGHAUS, OF BERLIN-CHARLOTTENBURG, GERMANY, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, OF YORK, N. Y., A

CORPORATION;

PROTECTIVE SYSTEM FOR TRANSMISSION LINES.

Application filed March 27, 1925, Serial No. 18,793, and in Germany Apri1 4, 1924.

My invention relates to protective systems for transmission lines and particularly to A protective systems for short-circuits or other is therefore increased in order to provide the necessary strength and capacity in all the current-carrying elements" thereot.

It has been proposed to insert impedances inthecircuit in order to limit the short-cir cuit current, but such impedances are disadvantageous because the cost of the installation is increased, the installation is rendered more complicated and the impedances represent a constant energy loss, even under normal conditions. e

In accordance with my inventiom'the system is simplified and normally no losses are incurred although ample protection isprovided against short circuits. My invention is applicable to feeders having considerable impedance, for example, by reason or their length and which are operated in parallel. If the current traversing the feeders exceeds a predetermined value, switches are automatically operated connecting the feeders in series relation thereby considerably in creasing the impedance or" the system. The operation of the switches is preferably elieeted by a current transformer in the feeder which is connected to an operating relay or coil of the switch. i

For a betterunderstanding of my invention, reference should be had to the accompanying drawings in which Fig. l is a diagrammatic view of an elec trical distribution system embodying my invention;

Fig.2 is a. similar view of a modification thereoi; and i h .Fig. 3ris a similar view of a modification in which no pilot-wire circuit is required.

Referring to Fig. 1, an electrical distribuswitches 5.

All of the conductors are connected through a conductor 4 to the supply bus 2. The load is connected to the system through the conductors3and 3 connected to the load bus.

Normally, thelines I, II and III are connected in parallel relation between the load and supply busses. However, it the switches 5 are open, the several lines are connected in series relation between the bosses. In order .to control the switches 5, a current transformer 6 is connected in the circuit adjacent to the load bus. so as to be energized in. accordance with they lead on the system. The secondary winding of the transformer G is connected throughthe pilot wire circuit 7 to the tripping coils ofthe switches 5. It desired, switches 8 and 8" ray be provided as indicated to open the circuit between the generating station and the supply bus or between the ipply and load busses. It is con1- HIOlliO pron automatic switches at these points. There 'e, the detailed circuits of the switches are not shown.

, I. a short-circuit devclopsin the load cir cuitaml excessbxe current traverses the system, the current translornrer 6 opens the The conduiictors I, II and III are then connected in series relation and limit the short-circuit currentby reason of the impedance of the conductors. In the ass of three conductors, as illustrated in Fl 2 1, the impedance of the circuit is increased to nine times the original value. Consequently the short-circuit current is limited to a value approximating that of the normal load and the conductors of the circuit and the switch 8 need only have sufficient capacity for this current. In some cases the short-circuit current is so reduced that it is unnecessary to open the circuit by the operation of the switch 8. Therefore, the continuity of service of the system is improved.

'lhe airi-angeinent which I have-described is simpler than the systems Which have been proposed heretofore and has greater eliiciency than a system using permanently con; ,nectedlreactors in the circuit. I The principal economy, however, is obtained in the reduction of the dimensions and capac ty of the. switchesbusses and lineconductors WlllCll is accomplished. 'I he first cost oi the installation is greatly reduced. j f

ls'ind'cated in Fig. 2, the system is applicableto feeders having'a greater numb-er of parallel conductors than 3; For example, if there are live parallel conductors 1,111,111, IV-fillCl V,-'tWo switches 5' are provided at each end-of the feeders; These switches all operated SnDUltfllROHSly' in the case of ashort-circuit, the operation being similar to that describedabove in connection with Fig. l. y In tllQCfiSG of systems h'avinglong feeders,

as indicated in Fig. 3 the pilotqvire circuit 'mayfbe eliminated in order to decrease "the cost of the'system. Referring to Fig. conductors I, II and III are connected to the bussesfl and 2 iii normally' parallel relation. Switches 5 and 5 are disposed in the conductor circuits to alter the normal parali lel-conne cted relation to a series connection,

' V asis 'obvious from the dranving. T

conductors.

" Q The switch o at the supplyend'of the co n-- ductors isactuated, uponthe occurrence of an'overload, by. meansjo t a circuit including a battery 9, or other suitable source of electromotive force, and the contacts of a relay 110; The Winding ot the relay, 10' may be energizedQfrom a transformer 6 associated with the supply conductor, in accordance Wit'n the power traversing" said conductor;

Similarly, at the load end of the conductors'L II and III, the siv'itch 5 is actuated by means of a batteryg'and is controlled by a relay 10 which is energized froin'a transformer 6 associated-With one of the parallel The operation'of this modification oi"- the invention is similarft'o that abovedescrihed,

but this modification is peculiarly adapted for installations wherein the lengths of the conductors I, II and III are such that the 5 use of pilot-Wire control circuits is undesirable from a cost standpoint V 7 Quite obv ously, various other modifications mayv be made n my invention Without operating-theswitching means in response to;

abnormal electrical conditions.

2.111 aiielectrical distribution system, a plurality of parallel transmission conductors, means for connectingsaidconductors to the system to. carry tlieload current in parallel and meansresponsive to an excessive current to reconnectsaid conductors in series relation to limit the flow of Current by; the series impedance thereof. 7 J

3. In'an electrical distribution system, a

supply bus, a reinote load bus,'a plurality Y or transmission conductors connecting said busses, switching means for connecting said conductors'in series or parallel 'relationa id means including a current transformer adjacent saidload bus for controlling said switchingmeans upon the occurrence of predetermined electrical conditions I 4. In an electrical dis'tributionsystem, a supply bus, a remote load bus, a plurality of transmission conductors connecting said busses, switching means adjacent each bus for connecting said conductors in series'or-pa-ralllel relation, a current transformer adjacent each bus and means. including saidftrans V formers for'coiitrollin'g the switching means upon 't'he occurrence of predetermined conditionsfl I i In testimony whereof I aiiix my signatureQ JOHANNES SESSINGHAUS. 

